Transmissions having a number of automatically selectable gears are typically controlled by a control circuit according to one or more pre-programmed shift schedules that define transmission shift points between the various gears as a function of engine speed. In some embodiments, the control circuit may have access to two or more different shift schedules that each defines transmission shift points according to different criteria. For example, a so-called economy mode shift point schedule may define transmission shift points at lower engine speeds relative to a so-called performance mode shift schedule such that relatively higher fuel economy is realized with the economy mode schedule and relatively higher engine performance is realized with the performance mode schedule.
One example criteria for selecting between two different shift schedules is vehicle mass such that under relatively lower vehicle mass conditions an economy mode shift schedule may be desirable, whereas a performance mode shift schedule may be desirable under relatively higher vehicle mass conditions. It is desirable to automatically determine a vehicle mass-based breakpoint for use in selecting between two different shift point schedules based on desired performance and on the current vehicle configuration, and to automatically re-determine the vehicle mass-based breakpoint if any one or more of these initial conditions changes.